The mummified remains of 15-month-old Declan Hainey, pictured, were found in his rubbish-strewn cot at the Paisley home he shared with his mother Kimberley in March 2010.

Former Johnstone resident Kimberley, 38, was jailed for murder over his death but was released last April after appeal judges quashed her conviction.

Speaking after Kimberley was cleared her mother, Renfrew resident Elizabeth Rodden, said she was “devastated” by the news.

The ruling by the three-judge panel at the High Court in Edinburgh means that little Declan’s death is now unexplained.

A Fatal Accident Inquiry into the child’s death is due to start at Paisley Sheriff Court next month to try to establish how the youngster died.

And, during a preliminary hearing this week, it emerged that a drug worker who had several meetings with Kimberley around the time of Declan’s death would have no participation at all in the case.

Despite being described as “a central witness in the inquiry” Dr Jacqueline Hague - who worked for Renfrewshire Drug Service - is being spared a stint on the witness stand because she is mentally ill.

Procurator fiscal Hugh Brady told Sheriff Ruth Anderson: “It is highly likely she will not be able to attend the inquiry or participate in any written statements and that is due to health reasons.” He said a report, which was made available to the sheriff, had been compiled by Dr Hague’s consultant psychiatrist, outlining Hague’s problems, which the court heard are of a “personal nature”.

She said the inquiry could proceed for the time being without the doctor and that a further decision could be made on Dr Hague’s attendance at another preliminary hearing next month.

He also asked eight lawyers - who were representing 17 individuals and organisations involved in the case - if they would agree the evidence of five witnesses to save them having to testify.

The evidence is expected to last for eight weeks and 48 witnesses are to take the stand.

Renfrewshire Council, Kimberley Hainey, Renfrewshire Council Community Health Partnership, two doctors, five health visitors and seven social workers will be represented at the inquiry, to begin on May 12.

A judgement is expected in August.